In the related art, due to a reduction in the size of an electronic device or an electric device, reductions in the size and the thickness of a part for electronic devices such as a terminal, a connector, a relay, and a lead frame used in the electronic equipment, the electric device, or the like have been achieved. Therefore, as a material of the part for electronic devices, a copper alloy having excellent spring property, strength, and electrical conductivity has been required. Particularly, as disclosed in Non-Patent Document 1, it is desirable that the copper alloy used in the part for electronic devices such as a terminal, a connector, a relay, and a lead frame has high proof stress and low Young's modulus.
Here, as the copper alloy used in the part for electronic devices such as a terminal, a connector, a relay, and a lead, for example, as disclosed in Patent Document 1, phosphor bronze containing Sn and P has been widely used.
In addition, for example, in Patent Document 2, a Cu—Ni—Si-based alloy (so-called Corson alloy) is provided. The Corson alloy is a precipitation hardening type alloy in which Ni2Si precipitates are dispersed, and has relatively high electrical conductivity, strength, and stress relaxation resistance. Therefore, the Corson alloy has been widely used in a terminal for a vehicle and a small terminal for signal, and has been actively developed in recent years.
In addition, as the other alloys, a Cu—Mg alloy described in Non-Patent Document 2, a Cu—Mg—Zn—B alloy described in Patent Document 3, and the like have been developed.